1. Field of the Invention
Embodiments of the present invention relate generally to disk drives and, more particularly, to disk drives having reduced magnetic flux leakage.
2. Description of the Related Art
Disk drives, and especially disk drives for mobile applications, are tightly constrained to simultaneously achieve low cost, low weight, and low power consumption. As higher performance, e.g., shorter seek time, and greater data capacity are demanded for such drives, satisfying cost, weight, and power requirements becomes increasingly difficult. This is particularly true for the voice coil motor (VCM) used in disk drives to position the read/write head over a desired data storage track.
When shorter seek times are desired, or the inertia of the head stack assembly is increased to enable higher drive capacity, the VCM must have higher torque. Because increased power consumption is generally not acceptable, higher torque is typically achieved by increasing the magnetic flux density in the VCM. Magnetic flux density can be increased by using a higher energy magnet material and/or by increasing the volume of the magnets. In either case, without other design changes to the VCM, the increased magnetic flux in the VCM produces a higher level of magnetic flux leakage outside the disk drive, which may be unacceptable.
Increased flux leakage from the VCM and, consequently, from the disk drive, is typically controlled with a larger return path or by creating additional return paths for the magnetic flux. Steel plates generally form the return paths for magnetic flux in a disk drive VCM, and increasing the width and/or thickness of such plates in high flux density areas can control flux leakage when higher energy or higher volume magnets are used. However, the addition of material to high flux density areas in the steel plates in a VCM results in undesirable VCM weight increases and will usually increase cost of the VCM. To offset such weight increases, weight is removed in other areas, adding complexity to the stamping process that is typically employed for fabricating the steel plates. In addition, removal of material from other areas of the steel plates creates design compromises that may reduce design margin, increase cost, and limit performance of the disk drive.
In light of the above, there is a need in the art for a means to reduce magnetic flux leakage from a disk drive without increasing weight or adding complexity to the manufacturing process.